Digital right management system, content server, and mobile terminal

ABSTRACT

A digital rights management system ( 1 ) includes a content server ( 30 ) that stores contents created by content creators, a mobile device ( 21, 22 ) that acquires and uses a desired content from the content server, and a data preservation server ( 40 ) that preserves the content used by the mobile device so as to enable the content to be uploaded and downloaded. The content server is configured to create rights information for the content, the rights information containing availability of backup saving of the content in the data preservation server, and to deliver the content and the rights information to the mobile device in response to a request from the mobile device. The mobile device is configured to create backup data when using the content based on the availability of backup saving and transmit the backup data to the data preservation server for preservation of the backup data.

FIELD OF THE INVENTION

The present invention relates to a technique for managing copyrightprotection of digital contents, and more particularly, to a digitalrights management system for managing creator's rights (including thecopyright) and the associated information in a mobile communicationnetwork, as well as to a content server and a mobile device used in sucha management system.

BACKGROUND ART

Unlike tangible entities such as industrial products or food products,digital contents are easily copied and reproduced in the originalstates. Although unauthorized or illegal reproduction (copying) ofcontents is banned under the Copyright Law, there are still manyunauthorized or illegal copies being made in reality. Robust protectionfor the copyrights of contents is a major concern of content creators,and is in serious demand.

In recent years and continuing, digital rights management (DRM), acopyright management technique for digital contents, has been attractingattention. At first, DRM techniques applied to music CDs, DVD videos, ordigital broadcasting came to the front, and then, the DRM techniqueapplied to mobile or cellular devices has been attracting much attentionalong with availability of a variety of types of contents and increaseof prices.

In response to the demand, standardization of DRM is being promoted bythe Open Mobile Alliance (OMA), which is a standards body for thetechnology of mobile software application elements. With OMA DRM,arbitrary contents delivered to mobile devices are to be protected bynot only restricting reproduction or copying of content under theprotection of the Copyright Law, but also allowing designation oflimitations (limited number of uses or expiration dates for use). TheOMA DRM is furnished with various functions responding to the demandsfrom contents providers, and one of such functions is asuper-distribution function enabling distribution of digital contents byseparating the copyright-protected contents from their rightsinformation.

There are two versions of OMA DRM, namely, OMA DRM version 1.0 (DRMv1.0,see Non-Patent Document 1 listed below), which is a basic technique forless expensive contents, and OMA DRM version 2.0 (DRMv2.0, seeNon-Patent Document 2 listed below), which is an advanced techniquetargeting expensive contents.

FIG. 1 is a schematic diagram illustrating the super-distributionfunction realized by the OMA DRM. With OMA DRM, the copyright-protectedcontent 1002 and the rights information (rights object) 1003 areseparated from each other, and delivered independently from each other.Super-distribution is a delivering scheme that allows free reproductionor redelivering of the content 1002, but values the rights information1003. The content 1002 is encrypted, and it cannot be used unless thecontent key contained in the rights information 1003 is acquired. A newcontent using scheme, in which the user transmits the encrypted content1002 to a friend by, for example, e-mail and the friend purchases therights information 1003 by himself (or herself), can be established.

The encrypted content 1002 is binarized according to the DRM contentformat (DCF). The DRM content format includes a URL of the rights issuer(RI) who holds the rights information 1003. The mobile device 1001accesses the URL of the rights issuer to request delivery of the rightsinformation 1003 that contains the content key. This arrangementrealizes distribution of digital contents, while protecting the digitalcopyrights through encryption.

Another known technique is a data management service system for cellularphones (see, for example, Patent Document 1 listed below). In thissystem, to remove inconvenience when the information and data used in anold cellular phone become unavailable when the old one is replaced witha new one, while maintaining protection of the copyrights of thecontents such as software applications, the information and data used ina cellular phone are stored in the data management server provided on anetwork. The information and data items furnished with author's(creator's) IDs are stored in the copyright protection area, and removalor transfer to another storage area is restricted. The data items storedin the copyright protection area can be downloaded only to the cellularphones associated with the protected data items. Accordingly, thecontents can be continuously available for the user even if the cellularphone is replaced with a new one because the information and data itemsare uploaded to and downloaded from the data management server asnecessary.

Still another known system is one that uses a license management server.If content downloaded from the network to a cellular phone is not usedfor a certain period, the license is sent from the cellular phone to bedeposited in the license management server on the network in exchangefor a certificate or a token. When the content is used again in thecellular phone, the license is acquired from the license managementserver based upon the certificate or the token. (See, for example,Patent Document 2 listed below).

Under the digital copyright management of the OMA DRM, unrestricteddistribution (including transmission) of contents is permitted, but therights information is prohibited from being freely distributed(including transmission from a cellular phone). If a cellular phone islost or broken after its content and the associated rights informationare acquired, the same content and the rights information have to beacquired again from the content provider. In addition, payment foracquiring the rights information may have to be made again, depending onthe situation.

When replacing a cellular phone with a new model, the cellular phone isconnected via a memory transfer device to an information processor toelectronically read the private data such as telephone numbers out ofthe memory and to write the data into the memory of the new cellularphone in the shop. To reproduce the contents under the copyrightprotection, licenses from the content creators are required. However,since it is not easy to obtain a license from each of the creators, therights information of the protected contents are not written into thenew cellular phone. This means that the user cannot continue to use thepurchased contents in the new cellular phone.

The data management service system disclosed in Patent Document 1 isdesigned such that whether to upload the content created by a contentcreator to the server is determined by the user. In fact, the user hasto obtain a license from the content creator or the author to reproducethe copyright-protected content for uploading to the server. However,this system cannot prevent malicious users from uploading or reproducingunauthorized contents in the server, and consequently, the reproductionright of the author is likely to be infringed.

In addition, this publication does not address the issue focused on therights information of the contents. Restriction on use of content (e.g.,limitation of number of uses or expiration date) may be designated inthe rights information of the content. Such restriction information isstatus information that changes every time the content is used. However,the conventional data management service system only handles the issuesoccurring in uploading and downloading data and information to and fromthe server, and it does not deal with the procedure required when thestatus information has varied along with use of the content. If thecellular phone is lost, the current limitation or restrictioninformation as to the use of the content cannot be taken over to a newcellular phone. For example, if up to five times use is permitted in therights information, and if the user has reproduced the content threetimes on the cellular phone, then two more uses are left for the user.However, there is no disclosure about how to deal with the statusinformation representing two more chances to reproduce the content beingleft. Thus, the status information cannot be correctly taken over whenthe cellular phone is replaced with a new one.

In the system of Patent Document 2 that supplies a license exchangecertificate or token to the cellular phone, the license exchangecertificate itself is lost if the cellular phone is lost, and therefore,the license deposited in the server cannot be returned to the cellularphone. This publication does not disclose procedures for reissue ortakeover of the license exchange certificate by the new cellular phone.After all, a new license has to be acquired.

-   -   [Non-Patent Document 1] Open Mobile Alliance, “OMA Digital        Rights Management Enabler Release”, Approved Version 1.0,        OMA-DRM-V1_(—)0-20040615-A, June 2004,        www.openmobilealliance.org.    -   [Non-Patent Document 2] Open Mobile Alliance, “OMA Digital        Rights Management Enabler Release”, Approved Version 1.0,        OMA-DRM-V2_(—)0-20040715-C, July 2004,        www.openmobilealliance.org.    -   [Patent Document 1] JP (Kokai) 2004-200845 A    -   [Patent Document 2] JP (Kokai) 2003-179590 A

SUMMARY OF INVENTION Problem to be Solved by the Invention

The present invention was conceived in view of the above-describedproblems, and it is one of the objectives of the invention to provide adigital rights management system that allows authorized digital content,the associated rights information, status information as to restrictionof use, and other necessary information to be continuously used in a newmobile device including a cellular phone, even if the old one is lost orreplaced. It is another one of the objectives of the invention toprovide a content server and a mobile device used in the digital rightsmanagement system.

Means for Solving the Problem

To achieve the objectives, rights information is created based onavailability of backup saving of each content, and backup datacontaining content using status information and rights information areproduced every time the content is used or reproduced in a mobiledevice. The produced backup data are stored and managed in a server on anetwork.

In the first aspect of the invention, a digital rights management systemcomprising a content server configured to store contents created bycontent creators, a mobile device configured to acquire and use adesired content from the content server, and a data preservation serverconfigured to preserve the content used by the mobile device so as toenable the content to be uploaded and downloaded is provided. In thissystem, the content server is further configured to create rightsinformation for the content, the rights information containingavailability of backup saving of the content in the data preservationserver, and to deliver the content and the rights information to themobile device in response to a request from the mobile device. Themobile device is further configured to create backup data when using thecontent based on the availability of backup saving and transmit thebackup data to the data preservation server for preservation of thebackup data.

In the second aspect of the invention, a mobile device used in theabove-described system is provided. The mobile device comprises:

-   (a) digital rights management means configured to acquire a content    and its associated rights information from a content server on a    network, manage the rights information and a using status of the    content, and determine availability of backup saving of the content    based on the rights information; and-   (b) backup means configured to create backup data containing the    using status of the content and the rights information in using the    content if it is determined that the backup saving of the content is    available, and save the created backup data in a data preservation    server on the network.

For example, the digital rights management means acquires the backupdata from a data preservation server upon input of a backup dataacquiring instruction.

In the third aspect of the invention, a content server is provided. Thecontent server comprises:

-   (a) a content saving unit configured to store a content created by a    content creator;

a determination unit configured to determine whether backup saving ofthe content is authorized;

-   (b) a rights information creating unit configured to create rights    information that contains a determination result as to availability    of the backup saving of the content; and-   (c) a content/rights information delivering unit configured to    deliver the content and the rights information in response to a    content acquiring request from a mobile device.

Preferably, the rights information includes a determination resultindicating availability of backup saving and an address of a datapreservation server for saving backup data of the content.

Advantages of the Invention

Even if a mobile device is replaced with a new one, previously availabledigital contents, the associated rights information, status informationas to restriction of use of the contents, and other necessaryinformation can be continuously used in the new device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration for explaining OMA DRM super-distribution;

FIG. 2 is a schematic diagram illustrating an example of a digitalrights management system according to an embodiment of the invention;

FIG. 3 is a sequence diagram illustrating an example of the processingprocedure performed in the digital rights management system shown inFIG. 2;

FIG. 4 is a schematic block diagram of a mobile device used in thesystem according to an embodiment of the invention;

FIG. 5 is a schematic diagram of a content server according to anembodiment of the invention;

FIG. 6 is an example description of OMA DRM rights information generatedby the content server;

FIG. 7 is an example of the data structure of the rights information;

FIG. 8 is a flowchart of updating the status information performed bythe DRM agent of the mobile device shown in FIG. 4;

FIG. 9 is a flowchart of creating backup data performed by the backupagent of the mobile device shown in FIG. 4;

FIG. 10 is an example of the data structure of the backup data createdby the backup agent; and

FIG. 11 is a flowchart of acquiring the backup data performed by the DRMagent of a new mobile device.

DESCRIPTION OF SYMBOLS

-   -   1: digital rights management system    -   21, 22: mobile device    -   30: content server    -   40: data preservation server    -   70: rights information    -   73: rights preservation availability information    -   80: backup data    -   201: DRM agent    -   202: data storage    -   203: backup agent    -   204: contents application    -   301: contents/rights information delivering unit    -   302: contents storing unit    -   303: rights information storing unit    -   304: backup saving availability determination unit    -   305: rights information creating unit

BEST MODE TO CARRY OUT THE INVENTION

The preferred embodiments are now described below in conjunction withthe attached drawings. In the figures referred to in the descriptionbelow, the same elements are denoted by the same numerical symbols.

(Overall System Structure)

FIG. 2 is a schematic diagram of a digital rights management system 1according to an embodiment of the invention. The digital rightsmanagement system 1 includes mobile devices 21 and 22, a content server30, and a data preservation server 40, which are connected to each othervia a network 10. Each of the mobile devices 21 and 22, the contentserver 30 and the data preservation server 40 has hardware resources,such as a CPU, memory/storage devices, and an input/output device, andsoftware resources stored in the storage.

The content server 30 holds arbitrary contents including images, motionpictures, music, and programs, and rights information about each of thecontents. The content server 30 may be split into two units based on thefirst function for holding the contents and the second function forholding the rights information, as in the OMA DRM system, oralternatively, these two functions may be combined into a single unit.In this embodiment, the contents and the associated rights informationare held in the content server 30.

When delivering content to the mobile device 21 or 22 in response to arequest, the content server 30 transmits the associated rightsinformation that contains an information item representing whetherreproduction of the content for the purpose of backup saving isauthorized by the copyright owner.

The mobile device 21 or 22 stores the content with authorization forbackup saving, together with the status information indicating the usingstatus, in the data preservation server 40.

The data preservation server 40 stores the data transmitted from themobile devices 21 and 22, and it supplies the stored data to the mobiledevices 21 and 22. In other words, the mobile devices 21 and 22 uploadand download data to and from the data preservation server 40.

FIG. 3 is a sequence diagram illustrating operations of the digitalrights management system 1 shown in FIG. 2. In this example, the userreplaces the mobile device A with a mobile device B.

The mobile device A transmits a request for acquiring a desired contentto the content server 30 (S101). The content server 30 creates rightsinformation, which information may include restricted usage, authorizednumber of uses and the expiration date designated by the content creatorhaving the copyright. The content server 30 adds an information item(backup saving availability flag) indicating whether backup saving ofthe content in the data preservation server 40 is available, to thecreated rights information (S102). Then, the content server 30 transmitsthe rights information, together with the requested content, to themobile device A (S103).

The mobile device A stores the acquired content and the associatedrights information (S104). Every time the content is used or reproduced,the status information including the remaining number of uses and timeto expiration is updated (S105), and backup data are generated (S106).The mobile device A transmits a request for saving the backup data tothe data preservation server 40 (S017). The data preservation server 40stores the backup data (S108).

When the user replaces the mobile device A with a mobile device B due toloss or model change (S109 and S110), the new mobile device B transmitsa backup data acquiring request to the data preservation server 40(S111). The data preservation server 40 authenticates that the mobiledevice B is owned by the same user as the mobile device A (S112), andtransmits the backup data to the mobile device B (S113).

Having acquired the backup data, the mobile device B extracts thecontent, the rights information, and the status information from thebackup data, and stores these data and information items (S114).

In this manner, the content server 30 creates for each of the contentsan information item indicating availability of backup saving in the datapreservation server 40 based on authorization of the copyright owner ofthe content, and adds the backup saving availability information to therights information. If backup saving is permitted, each of the mobiledevices 21 and 22 creates backup data that contains the statusinformation representing the status of the authorized right, and savesthe backup data in the data preservation server 40 every time thecontent is used. Consequently, even if an old mobile device is lost orreplaced with a new model, the new mobile device B can take over thelegally acquired content and the associated rights information as theyare.

FIG. 4 is a schematic block diagram of the mobile device 21 (or 22),which may be a cellular phone, a personal digital assistant (PDA), aportable notebook computer, or any other mobile terminal.

The mobile device 21 has a DRM agent 201, a data storage 202, a backupagent 203, and contents application 204.

The DMA agent 201 operates as an agent defined by OMA DRM. The DRM agent201 acquires a desired content and the associated rights informationfrom the content server 30, and manages the content using status basedon the descriptions of the rights information every time the content isused by the contents application 204.

The contents application 204 is used to offer the content to the user,and examples of the contents application 204 include music players,video viewers, and game applications.

The data storage 202 stores the content acquired by the DRM agent 201.The content or data stored in the data storage 202 is protected so as toprevent any access other than by the DRM agent 201.

When the content is used by the contents application 204, the backupagent 203 receives the data or information to be backed up from the DRMagent 201, and determines whether backup saving in the data preservationserver 40 is authorized for the received data. If backup saving isauthorized, the backup agent 203 creates backup data and transmits thebackup data to the data preservation server 40.

More detailed operations of the mobile device 21 will be describedlater.

FIG. 5 is a schematic block diagram of the content server 30. Thecontent server 30 has a content/rights information delivering unit 301,a content storing unit 302, a rights information storing unit 303, abackup availability determination unit 304, and a rights informationcreating unit 305. The content storing unit 302 stores contents createdby content creators. The rights information creating unit 305 createsrights information for each of the contents. The backup availabilitydetermination unit 304 determines whether backup saving in the datapreservation server 40 is authorized by the content creator having thecopyright for each of the contents, and supplies backup savingavailability information to the rights information creating unit 305.The rights information creating unit 305 adds the backup savingavailability information to the rights information. The rightsinformation storing unit 303 stores the created rights information inassociation with the corresponding content. Upon a request from themobile device 21 or 22, the content/rights information delivering unit301 delivers the requested content and the associated rights informationto the mobile device 21 or 22.

FIG. 6 illustrates OMA DRM information which is an example of the rightsinformation used in the embodiment. In OMA DRM, the rights informationis described using the extensible markup language (XML) based on opendigital rights language (ODRL). The rights information may includerestriction on usage of the content, the limited number of uses, and theexpiration date designated by the content creator or the copyrightowner.

FIG. 7 is an example of the data structure of the rights information 70created by the content server 30 and having backup saving availabilityinformation. In this example, the rights information 70 includesauthorized usage information 71, use restriction information 72, andrights preservation availability information 73 indicating availabilityof backup saving of the content.

Authorized use information 71 designates usage of the contents, such asreproduction, display, execution, or hardcopy, authorized by the contentcreator or the copyright owner. The use restriction information 72includes, in this example, the authorized number of uses, start time ofthe authorized use period, ending time, expiration time from the starttime, and absolute expiration time (one week from acquisition ofcontent).

Rights preservation availability information 73 includes a rightspreservation availability identifier 74 that indicates whether theassociated content is permitted to be saved in the data preservationserver 40, and address information 75 that indicates the address of thedata preservation server 40.

The rights preservation availability identifier 74 has four informationitems; content, rights information of the content, status informationabout the rights information, and annex information, where each of theitems has an indication whether backup saving is permitted. For example,if backup saving is possible, a flag is set for the associatedinformation item. The annex information has a sub-item, such as ascratch pad or other memory information. The sub-item also has anindication about availability of backup saving. The content informationin the rights preservation availability identifier 74 is for the contentacquired by the mobile device 21 or 22 from the content server 30. Therights information is one associated with the content. The details ofthe status information about the rights information and the annexinformation will be described below.

The data preservation server address 75 denotes the address of the datapreservation server 40 accessible from the mobile devices 21 and 22 foruploading and downloading data.

For example, when arbitrary content is registered in the content server30, the content server 30 queries the content creator as the copyrightowner whether reproduction of the content can be authorized for thebackup purpose. If reproduction for the backup purpose (that is, backupsaving in the data preservation server 40) is authorized, the flag ofthe item “content” managed under the rights preservation availabilityidentifier 74 of the rights information 70 is set “YES”. Ifauthorization cannot be obtained from the content creator (copyrightowner), the flag of the item “content” managed under the rightspreservation availability identifier 71 is set “NO”. The content creatorhaving the copyright can designate a server in which the backup data areto be preserved, using the server address.

FIG. 8 is a flowchart of the updating operations of the statusinformation carried out by the mobile device 21 (or 22) during the useor reproduction of the content downloaded from the content server 30.Prior to the operation flow, the DRM agent 201 of the mobile device 21acquires a desired content and the associated rights information fromthe content server 30 in response to the user's instruction, and storesthem in the data storing unit 202. The stored content and the rightsinformation are managed so as to be inaccessible except from the DRMagent 201.

Upon an instruction from the user to use the content (YES in S11), theDRM agent 201 takes the content and the rights information out of thedata storing unit 202, and performs a necessary process to decode thecontent into the executable state. The decoded content is supplied tothe contents application 204.

When the content is used through the contents application 204, the DRMagent 201 updates the status information to monitor the using status ofthe content (S12). The status information represents the intermediarystate of the content using process, and this information is necessary tocorrectly deal with the content in complying with the restriction on theusage designated in the rights information 70. The status informationincludes the remaining number of uses, time validity information, andother necessary information. The remaining number of uses is a valuecalculated by subtracting the number of actual uses of the content fromthe authorized number of uses designated in the rights information. Thetime validity information includes time to the expiration represented byat least one of the information items selected from ending time, periodof validity from the start time of using the content, and the absoluteexpiration time contained in the rights information. The statusinformation is updated every time the content is used.

When the status information has been updated, the DRM agent 201determines whether the content, the rights information of the content,the status information about the rights information, and the annexinformation can be transmitted to the data preservation server 40 (S13).To be more precise, the DRM agent 201 checks the descriptions in therights preservation availability identifier 74 to determine which of theinformation items among the content, the rights information, the statusinformation, and the annex information is/are permitted to be backed upin the data preservation server 40. For example, if the informationitems “content” and “rights information” represent availability (“YES”),it means that the content creator (copyright owner) has agreed torestricted reproduction of the content and the rights information forthe backup purpose.

If there are any information items in the rights preservationavailability identifier 74 indicating authorization for backup saving inthe data preservation server 40 (YES in S13), the DRM agent 201 suppliesinformation about which items are to be backed up in the backup agent203 (S14).

FIG. 9 is a flowchart showing the operations of the backup agent 203 ofthe mobile device 21 (or 22). Upon receiving the information aboutbackup from the DRM agent 201 (S21), the backup agent 203 creates backupdata (S22).

FIG. 10 is an example of the data structure of backup data 80. In thisexample, the backup data 80 include mobile device information 81,content basic field 82, content field 83, content rights informationfield 84, status information field 85, and annex field 86. The mobiledevice information 81 contains ID information of the mobile devicecreating the backup data 80. The content basic field 82 contains thecontent ID unique to each of the contents, and content type specifyingthe media type of the content. The content field 83 contains the contentitself. The content rights information field 84 contains the rightsinformation of the content. The status information field 85 containsstatus information representing the using state of the content managedby the DRM agent 201. The annex field 86 contains other relatedinformation. Those information items not being transmitted to the datapreservation server 40 may not be contained in the backup data 80.

Examples of the related information of the content contained in theannex field 86 include, for example, scratch pad when the content is aJava (registered trademark) application for cellular phones. The scratchpad is a memory area in which the progress of a game is recorded whenthe game is interrupted. When the game is resumed, the recorded data areread out of the scratch pad.

Returning to FIG. 9, when the backup data have been created, the backupagent 203 transmits the backup data to the data preservation server 40(S23). It is unnecessary for the backup agent 203 to newly create andtransmit all the fields of the backup data 80 every time backup isrequired. For example, every-time transmission of the scratch pad in theannex field 86 leads to undesired consumption of the network resourcesbecause of the increased size. Accordingly, it is desired not to includethe data unnecessary to be transmitted to the data preservation server40 in the backup data 80.

Upon receiving the backup data from the mobile device 21, the datapreservation server 40 authenticates the mobile device 21. Toauthenticate the mobile device 21, the password, the telephone numberserving as the identifier of the mobile device 21, an internationalmobile subscriber identity (IMSI), or an electronic certificate may beused. The data preservation server 40 has a data preservation area tosave data under each mobile device identifier, and the backup datatransmitted from the mobile device 21 is stored in the correspondingblock of the data preservation area. Access to this block from any otherdevice is prohibited, and only the mobile device 21 can access theblock.

If the mobile device 21 is replaced with a new mobile device 22, the newmobile device 22 acquires the backup data from the data preservationserver 40.

FIG. 11 is a flowchart of the operations performed by the new mobiledevice 22 to acquire the backup data. Upon instruction from the user toacquire certain content, the DRM agent 201 of the new mobile device 22acquires the content and the associated rights information from thecontent server 30 (S31). The DRM agent 201 stores the content and therights information in the data storage 202, and manages these items soas to be inaccessible except from the DRM agent 201.

When an instruction to acquire the backup data is input by the user (YESin S32), the mobile device 22 transmits a request for the backup data,together with the ID information of the old mobile device 21 (S33).

Upon receiving the request for the backup data from the mobile device22, the data preservation server 40 authenticates the mobile device 22,and determines whether there is backup data existing in the blockmanaged under the identifier of the old mobile device 21 in the datapreservation area. Two or more backup data items may be stored. If thereare any backup data in the corresponding block in the data preservationarea, the data preservation server 40 transmits the backup data items tothe mobile device 22.

The DRM agent 201 of the mobile device 22 receives the backup data fromthe data preservation server 40, and takes information items out of thebackup data to store them in the appropriate section. The content andthe associated rights information are stored in the data storage 202.The status information is managed by the DRM agent 201. The memoryinformation recorded in the annex field of the backup data is taken inas the memory data of the mobile device 22 (S34).

With this operation flow, the previously used information items,including a digital content, the rights information of the digitalcontent, the status information representing the using status of thecontent, and other related information can be continuously used in a newmobile device even if the old mobile device is replaced by the user withthe new one to change the model or after the old device is lost.

Finally, some consideration is made for security. The backup datatransmitted between the mobile devices 21, 22 and the data preservationserver 40 has to be protected from interception by a third party.Accordingly, an appropriate process has to be provided for thecommunications between the data preservation server 40 and the mobiledevices 21, 22 to keep the communications secret. For example, IPSec (IPsecurity) or SSL (secure socket layer) may be employed as typicalsecurity.

The data preservation server 40 needs to authenticate the mobile devices21 and 22 when accessed from these devices. In authentication, thepasswords, the telephone numbers serving as identifiers of the devices,the international mobile subscriber identities (IMSIs), or theelectronic certificates may be used, as has been described above.

The data preservation server 40 may work with the content server 30 asnecessary when confirming whether the mobile devices 21 and 22 areauthorized to use the data preservation server 40. In this case, thecontent server 30 records identifiers of the mobile devices 21 and 22when creating the rights information for these devices. The datapreservation server 40 queries the content serve 30 about the identifierof a currently accessing mobile device. The data preservation server 40then receives a replica of the rights information issued to the mobiledevice from the content server 40 if the mobile device is authorized,and determines that the currently accessing mobile device is authorizedto use the data preservation server 40.

This international application is based upon and claims the benefit ofthe earlier filing date of Japanese Patent Application No. 2005-138957filed May 11, 2005, the entire contents of which are hereby incorporatedby reference.

1. A digital rights management system comprising: a content server configured to store contents created by content creators; a mobile device configured to acquire and use a desired content from the content server; and a data preservation server configured to preserve the content used by the mobile device so as to enable the content to be uploaded from the mobile device and downloaded to a respective mobile device; wherein the content server is further configured to create rights information for the content, and to deliver the content and the rights information to the mobile device in response to a request from the mobile device, the rights information containing availability of backup saving of each of the content, the rights information of the content, status information of the rights information, and annex information; and the mobile device is further configured to create backup data of an authorized one of the content, the rights information of the content, the status information of the rights information, and the annex information when using the content based on the availability of backup saving and transmit the backup data to the data preservation server for preservation of the backup data.
 2. A mobile device comprising: digital rights management means configured to acquire a content and its associated rights information in which availability of backup saving of each of the content, the rights information of the content, status information of the rights information, and annex information are described from a content server on a network, manage the rights information and determine availability of backup saving of each of the content, the rights information of the content, the status information of the rights information, and the annex information, based on the rights information; and backup means configured to create backup data items of an authorized one of the content, the rights information of the content, the status information of the rights information, and the annex information, when using the content, and upload the created backup data in a data preservation server on the network, the data preservation server configured to preserve the content used by the mobile device so as to enable the content to be downloaded to a respective mobile device.
 3. The mobile device of claim 2, wherein the digital rights management means acquires the backup data from the data preservation server upon input of a backup data acquiring instruction.
 4. The mobile device of claim 2, wherein the rights information contains description about restriction on use of the content.
 5. The mobile device of claim 2, wherein the backup means includes annex information produced as a result of use of the content in the backup data if it is determined that the rights information indicates the availability of backup saving of the annex information.
 6. A content server comprising: a content saving device configured to store a content created by a content creator; a determination unit configured to determine whether backup saving of the content is authorized; a rights information creating unit configured to create rights information that contains a determination result as to availability of the backup saving of each of the content, the rights information of the content, status information of the rights information, and annex information; and a content/rights information delivering device configured to deliver the content and the rights information in response to a content acquiring request from a mobile device, wherein the backup saving of each of the content is performed at a data preservation server configured to preserve the content used by the mobile device so as to enable the content to be uploaded from the mobile device and downloaded to a respective mobile device.
 7. The content server of claim 6, wherein the rights information includes a determination result indicating availability of backup saving and an address of an data preservation server.
 8. A digital rights management method, implemented on a content server, comprising the steps of: registering a content created by a content creator; determining whether backup saving of each of the content, rights information of the content, status information of the rights information, and annex information is authorized; creating the rights information for the content, the rights information containing a determination result as to availability of the backup saving of each of the content, the rights information, the status information of the rights information, and the annex information; and delivering the content and the rights information in response to a content acquiring request from a mobile device, while managing the content and the rights information on a network, wherein the backup saving of each of the content is performed at a data preservation server configured to preserve the content used by the mobile device so as to enable the content to be uploaded from the mobile device and downloaded to a respective mobile device.
 9. A digital rights management method, implemented on a content server, comprising the steps of: acquiring a content and associated rights information from a content server on a network, the rights information containing availability of backup saving of each of the content, the rights information, status information of the rights information, and annex information; determining whether backup saving of each of the content, the rights information, the status information of the rights information, and annex information is authorized based on the rights information when using the content; creating backup data of an authorized one of the content, the rights information, the status information of the rights information, and the annex information, and uploading the backup data in a data preservation server on a network, the data preservation server configured to preserve the content used by the mobile device so as to enable the content to be downloaded to a respective mobile device. 